This invention relates to an improvement in an external combustion engine, suitable for use in vehicles. The engine employs an organic Rankine cycle.
Steam cars represent one of the earliest applications of external combustion engines to motor vehicles. The Stanley brothers, Francis E. Stanley and Freelan O. Stanley, pioneered the commercialization of steam cars in the United States. In 1906, a steam powered vehicle constructed by the Stanley Steam Motors Corporation set a world speed record of 127.66 mph. Another innovator in the field of external combustion engine powered vehicles was Abner Doble. His improvements to steam power plants may be found in U.S. Pat. No. 1,675,600; U.S. Pat. No. 2,379,887; U.S. Pat. No. 2,393,313; and U.S. Pat. No. 2,440,328. The external combustion engine was eclipsed, however, by the widespread adoption of the internal combustion engine.
Nevertheless, work has continued over the years to develop the external combustion engine for automobiles. An automobile incorporating an organic refrigerant as the motive or working fluid, rather than water, is disclosed in an article entitled New: Minto's Unique Steamless “Steam” Car, appearing in Popular Science, Volume 197, No. 4 (October 1970). A fluorocarbon refrigerant, R-113, having a boiling temperature of approximately 117° F. (47.2° C.) was identified as the preferred organic fluid. Wallace L. Minto obtained several patents on his inventions, including U.S. Pat. No. 3,479,817, U.S. Pat. No. 3,750,393, and UK Patent No. 1 303 214. The motor for converting the movement of the fluid to mechanical energy comprised fluted rotors, having flutes of different size, such as may be found in air compressors.
One of the drawbacks of powering a vehicle with an external combustion engine, especially a personal automobile, has been the engine's characteristic slow starting. For example, when a vehicle is not operating, the working fluid will gradually cool to ambient temperature, which in the summer months may be 40° C., but in the winter months may be −20° C. or lower. Consequently, when the engine is started, there is a delay in transferring heat energy from the combustion gases of the fuel to the working fluid, sufficient to raise the temperature and pressure of the working fluid to operating levels.
Another drawback of the external combustion engine is experienced when one desires to operate the vehicle for only a brief period of time, such as when rearranging cars in a parking lot. There is a large expenditure of fuel required to bring the working fluid up to operating levels, and the heat energy is lost when the vehicle is turned off and the working fluid cools to ambient temperatures.
The Rankine cycle has been disclosed for use in conjunction with an internal combustion engine (ICE) or fuel cell, to generate work from waste heat. In Kubo et al., U.S. Pat. No. 4,901,531, waste heat from an ICE is used to generate a pressurized working fluid capable of driving a piston. Lee et al., U.S. Pat. No. 6,902,838 B2, disclose using waste heat from a fuel cell to generate a pressurized working fluid to drive a shaft. In Minemi et al., U.S. Pat. No. 6,910,333 B2, waste heat from the engine is recovered with first and second Rankine cycles.
The organic Rankine cycle engine has been used to generate electrical energy from waste heat, geothermal heat or solar generated heat. Examples of such applications include U.S. Pat. No. 6,101,813; U.S. Pat. No. 5,038,567; and U.S. Pat. No. 4,942,736. Generally, such uses relate to stationary power generation, and the aforementioned shortcomings of external combustion engines are not addressed.